ios 首先获取系统当前时间：

首先获取系统当前时间：

NSCalendar *cal = [NSCalendarcurrentCalendar];

unsigned int unitFlags = NSYearCalendarUnit |NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit |NSMinuteCalendarUnit | NSSecondCalendarUnit;

NSDateComponents *dd = [calcomponents:unitFlags fromDate:date];

int y = [dd year];

int m =[dd month];

int d = [dd day];

int h = [dd hour];

int m = [dd minute];

int s = [dd second];

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NSDateFormatter使用示例：

NSDateFormatter * dateFormatter =[[[NSDateFormatter alloc] init]autorelease];

[dateFormatter setAMSymbol:@"AM"];

[dateFormatter setPMSymbol:@"PM"];

[dateFormatter setDateFormat:@"dd/MM/yyyyhh:mmaaa"];

NSDate *date = [NSDate date];

NSString * s = [dateFormatterstringFromDate:date];

显示效果为：15/08/201116:20PM

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附上一些常用的格式：

yyyy:MM:dd G 'at' HH:mm:ss zzz 1996.07.10 AD at 15:08:56PDT

EEE, MMM d, "yy Wed,july 10, '99

h:mm a 12:08PM

hh 'o"clock' a,zzzz 12 o'clockPM, Pacific Daylight Time

K:mm a, z 0:00 PM, PST

yyyyy,MMMM.dd GGG hh:mm aaa 01996.july.10 AD 12:08PM